A traditional hard-telescope endoscope includes an object lens system, a turning lens system, an eyepiece lens system, and a telescope. Optical images transmitted from the object lens system can be displayed on a display after being processed by an optical system, which is usually located at the front telescope of the endoscope. Due to the long optical transmission distance of an optical image, this type of endoscope provides poor quality images.
To shorten the transmission distance of optical images and improve the image quality, there is a prior art electrical endoscope comprising an object lens, a charge coupled device (CCD) image sensor, a flexible circuit board, a telescope, and an operation system. According to the electrical endoscope, the optical signals from the object lens are converted to electrical signals by the CCD image sensor in the telescope, and processed to be displayed on the display. This endoscope can avoid the signal loss caused by the long distance of optical signal transmission and provide better quality images. But in order to position the object lens, CCD image sensor and multiple flexible circuit boards accurately, it is necessary to fill the telescope with adhesive and employ multiple connectors, resulting in a complicated structure and high manufacturing cost.